Refactor RangeBoundary +/- infinity to be distinct RangeBoundary kinds.

runtime/vm/intermediate_language_arm64.cc

Index: runtime/vm/intermediate_language_arm64.cc
diff --git a/runtime/vm/intermediate_language_arm64.cc b/runtime/vm/intermediate_language_arm64.cc
index da4e8b84660b4bbcc663c2fe7f9b2300bde7b54f..3839adcfe8fb3c4c6e07e5050fbaa9fd72f16606 100644
--- a/runtime/vm/intermediate_language_arm64.cc
+++ b/runtime/vm/intermediate_language_arm64.cc
@@ -2579,8 +2579,7 @@ static void EmitSmiShiftLeft(FlowGraphCompiler* compiler,
   if (is_truncating) {
     if (right_needs_check) {
       const bool right_may_be_negative =
-          (right_range == NULL) ||
-          !right_range->IsWithin(0, RangeBoundary::kPlusInfinity);
+          (right_range == NULL) || right_range->IsNegative();
       if (right_may_be_negative) {
         ASSERT(shift_left->CanDeoptimize());
         __ CompareRegisters(right, ZR);
@@ -2913,7 +2912,7 @@ void BinarySmiOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
       // sarl operation masks the count to 6 bits.
       const intptr_t kCountLimit = 0x3F;
       if ((right_range == NULL) ||
-          !right_range->IsWithin(RangeBoundary::kMinusInfinity, kCountLimit)) {
+          !right_range->OnlyLessThanOrEqualTo(kCountLimit)) {
         __ LoadImmediate(TMP2, kCountLimit, PP);
         __ CompareRegisters(TMP, TMP2);
         __ csel(TMP, TMP2, TMP, GT);